Initially, the authors showed that supernatants from cells cultures undergoing various forms of cellular death (freeze-thaw, cisplatin, etoposide or ATP + LPS combination) rather than inducing TNF-α from macrophages it could actually suppress macrophage's response to a canonical inflammatory stimulus such as gram-negative bacterial wall-derived endotoxin, LPS.

Since supernatants treated with DNase I, RNase A, proteinase K or trypsin retained its suppressive activity on the LPS induced production of TNF-α, the authors focus on lipids. Indeed, lipid cellular fraction could reproduce inhibitory effect of the necrotic cell supernatant.

Next, they found that PGE2 was highly enriched in these supernatants and could mediate its suppressive effect.

Synthesis of PGE2 is catalyzed by two cyclooxygenase enzymes, COX-1 and COX-2. Pre-treatment of cells with indomethacin, an inhibitor of COX-1 and COX-2 enzymes, reduced suppressive effect of necrotic cell supernatant.